I find the timing marks to be very vague on that shifting plastic housing. Every time I replace the belt I mark the belt and pully's then transfer to the new belt. If it ran decent before it was assumed correct. The "tune" switch is actually factory. Off is for regular gas and On is for Premium gas and it controls the boost (maybe timing and fuel too???).
As to the Ranger cam, it actually has less lift than the factory slider cam. I believe the results (air flow) come out similar because the roller aspect allows for a "fatter" cam where the duration may be similar but at any given point (for the most part) it is at a higher lift on the ramp. I hope I didn't confuse you. The lift on the roller is lower overall but MOST of the way up the ramp it is higher at a matched duration to the slider cam. That is something the roller allows for that would likely be excessive on a slider cam. At least that is what I have been told.
My '73 wagon has a similar set up as yours. '88 T/C engine (stock otherwise) and a T-5 with 3.40 gears and 205-60-13 tires. Even with the smaller IHI turbo (and it is even smaller than earlier turbos to spool up faster) it is like a N/A engine until the boost comes on. And it only comes on with a heavy foot around 2,500-3,000 RPM. And frankly there isn't much past 4,500-5,000 RPM. From my experience the "fun" (so to speak) with the turbo motor comes from a slow, steady pressing of the throttle after shifting out of the "granny" 1st gear. It seems to respond like a stock N/A engine at the beginning but at some point the boost feels like the car is rapidly gathering speed. Unfortunately by 5,000 RPM the E-Ticket ride is shortly over and you need to shift.
Originally I had 3.00 gears and 215-60-14" tires. Honestly from a performance perspective it was more enjoyable to drive. You stayed in a given gear much longer and you could feel that "gathering speed" aspect for a much longer time between shifts. And the car never felt any slower for it. However, on the surface streets at posted speed limits the car never seemed to have the right gear. One gear was too low and the next up was too much bog. So, That is why I went to the 3.40 and 205-60-13" tires. Everyday driving is far better now but the performance aspect is as stated above where the car blips in and out of boost for the all too soon shift. It seems you can have one, but not the other.